Over the past couple of weeks I have encountered problems receiving C31 Digital. I live in Ormond in an apartment block and currently use a Tandy/Dick Smith indoor VHF/UHF antenna with booster. Until recently I have been receiving all digital channels in Melbourne no problems at all. Then I noticed that my C31 picture is either heavily pixelated, static or has no signal. All other channels are not affected and can still be received clearly. Does anyone else have this problem?

In answer to your questions:
(1) I get my TV reception from Mt Dandenong
(2) I do have a master antenna system but it is very old (ribbon), the antenna is hidden in the roof and only receives 2, 7, 9 and 10 analogue.

Why can't they have the same power as other stations? They will need to if they are going to cover all of Melbourne.
As I said before I used to get C31 in digital but not anymore. It seems that C31 has lowered the power on their digital transmitter.
An outside antenna is not an option as it costs a lot of money for a 10-unit block, reception in this part of Melbourne requires fringe-area antennas, and it involves a lot of body corporate red tape.
Also, why doesn't Foxtel carry C31

Breakfast of champions,
The power of the channel 32 transmitter has always been a lot less than the equivalent which is SBS. The point is that not all of Melbourne/Geelong can receive this signal. The only community TV transmitter which is the same power as SBS is West TV in Perth. The reason why they have less power is the cost of purchase and running transmitter increases with power.

All analog TV transmitters in Melbourne will be switched off at the end of next year.

You do not say how many apartments are in your building and whether it has a single owner or if it's strata title.

Breakfast of champions,The power of the channel 32 transmitter has always been a lot less than the equivalent which is SBS. The point is that not all of Melbourne/Geelong can receive this signal. The only community TV transmitter which is the same power as SBS is West TV in Perth. The reason why they have less power is the cost of purchase and running transmitter increases with power.

All analog TV transmitters in Melbourne will be switched off at the end of next year.

You do not say how many apartments are in your building and whether it has a single owner or if it's strata title.

Given the age of the cabling (coax cable was introduced when colour TV commenced in Australia in 1975) the antenna may also be very old and not suitable for the digital channels and possibly only designed for VHF.

It would be a reasonable assumption that other residents would also be experiencing poor digital reception from the MATV system and it would be beneficial to all to have the antenna and distribution system ugrded to digital standard.

The cost should be divided among the 10 owners.

Other options you could try is moving your indoor antenna around the room. You may need an RG6 Quadshield extension cable to move it away from the TV.

You could also try tuning the Como frequencies, but keep in mind C31 from Como is very low power.

As usual Alan has taken a little bit of information and knowledge and run with it in completely the wrong direction!

Yes, the CTV services are operating at a lower ERP than the SBS but they are also operating with a much more robust modulation mode which effectively provides the same coverage! Possibly there are some cost considerations but it is really that the government has only allowed the CTV licensees to provide one program stream which only requires a limited bitrate.

I'm not an installer and could summise that your change in reception could be due to changes in trees, foliage, weather, your antenna system, local interference but the only way to really know is to get an installer out to check.

Also note that Alan is guessing that the CTV services will continue post analog restack and shift to VHF channels or carriage with the SBS. This may happen but is certainly not guaranteed. Alan's often been criticised for posting from a position of certainty when in fact he is an armchair expert making (possibly) educated guesses!

I suspect Alan will come back wanting to debate with me but I'm not trying to enter a debate, just give some balance to his "advice".

I'm often amazed by the performance in regard to BER/MER of those channels, which in some cases is far superior to all other networks, regardless of transmission power.

You're probably aware of it, but compare the modulation parameters of the community channels to the national broadcasters sometime. Briz31, last I looked, was using QPSK (and, IIRC, a guard interval of 1/8), which is a helluvalot more robust than QAM64 & 1/16.

(edit: And I see that's been covered [and argued about, as per usual ]. Serves me right for only looking at the last post in the thread!)

CWULF
Firstly after the digital restack the only RF channels to be used in state capital cities are;
Channel 6 carrying the 7 network
Channel 7 carrying SBS
Channel 8 carrying Nine network
Channel 9 DAB+ radio
Channel 9A DAB+ radio (not used in capital cities but surrounding areas)
Channel 10 Unallocated
Channel 11 carrying the TEN network
Channel 12 carrying the ABC.
The ACMA is going to change SBS to 64 QAM when they move to channel 7. Since the only community TV stations are in mainland state capital cities it is entirely possible that they may be added to the capital city SBS feeds to use their spare capacity. This will leave channel 10 and its UHF equivalents free for a nationwide network.
Other restack groups are
Group B channels 28 - 33 inclusive
Group C channels 34 - 39
Group D channels 40 - 45
Group E channels 46 - 51
On any individual site the same polarisation is used for all 6 transmitters. Sites may be vertical or horizontal polarisation.

The commercial DTV rollout is all using the above channel groups. Some ABC/SBS channels may need to change channels.

Search digital restack on the ACMA site if you don't believe it.

As for the relationship between power and QPSK/64 QAM. The first thing which a receiver must do is to detect and measure the pilot frequencies in the signal. If the power is insufficient then it is irrelevant what type of modulation is used. If the pilot cannot be used to lock the decoding clock the modulation type is irrelevant. Once this lock occurs then QPSK only has 4 phases of full modulated power, whereas 4 levels of power in 4 phases gives 64 states.

So as I have said once the receiver is locked on a signal then there is much better noise immunity using the low capacity QPSK. However if the signal field strength is too weak no reception is possible.

The field strength is 11 dB lower than SBS for MGV32 and for South Yarra MVG66 it is also 11 dB lower than the other transmitters.
AlanH